The latest UK national audit reported a risk of malignancy (ROM) of 27% for Thy3a nodules. This is equivalent to Thy3f ROM of 26.9%. Thy3a may be overtreated with diagnostic surgery if ROM is confounded by unrelated incidental thyroid cancers. Preoperative ultrasound, and postoperative histopathology can be correlated to confirm any confounding lesions. Our aim was to investigate the ROM of Thy3a nodules at a tertiary referral cancer centre.

295 patients with preoperative Thy3a FNAC between January 2015 and December 2022 were retrospectively reviewed. The study was registered as an audit. Demographic, radiologic, cytologic and histopathologic data were extracted from electronic health records.

Age ranged from 11 to 89 years. 81% were females (239/295). 43.7% (129/295) of patients underwent surgery. A final histopathological diagnosis was available for 126 patients, with an overall rate of cancer of 40.5% (51/126). When correlating size and location of Thy3a nodules between preoperative ultrasound and postoperative histopathology, the actual ROM of Thy3a nodules in patients operated on was 28.6% (36/126). Of these, 14/36 were classical papillary thyroid carcinoma (PTC), 12/36 follicular thyroid carcinoma , 6/36 follicular variant of PTC, 2/36 classical +follicular variants of PTC, 1/36 medullary thyroid carcinoma and 1/36 anaplastic +PTC

Compared with national data, Thy3a ROM was slightly higher at our centre. Correlation and exclusion of any cancers in other nodules did not reduce ROM. We propose ultrasound and histology correlation in a larger cohort to confirm if high ROM. This might warrant change in management of Thy3a nodules